The present invention relates to electronic watermarking technology for embedding information in contents such as images or music, in a practically visually or audibly indiscernible manner, and particularly relates to electronic watermark inspecting technology for inspecting electronic watermarks embedded in various types of contents such as pictures, music, broadcast programs, and so forth.
More specifically, the present invention relates to electronic watermark inspecting technology for judging whether or not making duplicates of contents is permissible according to the results of inspections of electronic watermarks embedded in contents, and particularly relates to electronic watermark inspecting technology wherein electronic watermark inspecting processing with heavy computation loads is performed vicariously.
A copyright is a relative exclusive right to the use of copyrighted material, and is a type of intangible property rights. The term “copyrighted material” as used here refers to creative expressions of ideas or emotions, pertaining to the realms of literature, science, art, or music. Copyrights are protected by the copyright laws in each nation, and by international treaties such as the Berne Convention for the Protection of Literary and Artistic Works, the Universal Copyright Convention, and so forth. For example, digitized text, computer programs, digitized music contents, picture contents, broadcast program contents, and like media are also copyrighted material, and should be appropriately protected under copyright laws.
It is extremely rare that only the copyright holder of copyrighted material exercises use thereof, usually the copyright holder gives permission for another party to use the copyrighted material, for a set price. Accordingly, in order to guarantee protection of copyrights, it becomes necessary to prevent unauthorized use of copyrighted material by others such as making duplicates of the copyrighted material without permission.
The history of copyright protection dates back to the 15th century, and is said to have originated with the invention of the art of printing. However, the tremendous advancements in electric and electronic arts in recent years has facilitated duplication of copyrighted material, and accordingly the state of matters regarding copyrights has been constantly changing.
Duplicating or tampering with data or contents in digital format is extremely easy, to the extent that it may be said that such data or contents are nakedly exposed to the danger of copyright infringement. Accordingly, simply making copyright laws or other such legal restrictions tougher is insufficient, and there seems to be a need to support authorized use of copyrighted material of eliminate unauthorized use thereof from a technological perspective, thereby increasing protection of copyrights.
One example of means for combating unauthorized copying in the field of digital contents is the “electronic watermark” technology, also known as “digital watermarking” or “data hiding”. An “electronic watermark” means embedding information in contents such as images or music in a practically visually or audibly indiscernible manner (e.g., see “Data Hiding Technology supporting Electronic Watermarking (parts 1 and 2), carried in the Feb. 24 and Mar. 10, 1997, issues of Nikkei Electronics).
For example, in 1998, a group centered around major USA record companies established a forum called SDMI (Secure Digital Music Interactive). SDMI stipulates a function called “screening”, as a system for protecting copyrights with portable music players. Screening consists of a system for inspecting on a memory recorder of a portable device whether or not copying of the contents is permissible or not, and an agreement has already been reached to use electronic watermarking. Electronic watermarking can be used to screen such that no more copies can be made from contents illegitimately distributed or from contents already copied once (or a predetermined number of times), for example.
FIG. 1 illustrates a function block diagram for performing screening processing as envisioned by SDMI. As shown in the figure, music contents read from recording media such as a CD or MD, of music contents received via communication medium, is first subjected to screening (i.e., inspected for electronic watermark), thereby checking whether or not copying thereof is permissible, following which the contents are subjected to compression enciphering with a system called LCM (Licensed SDMI Compliant Module) and then copied to the portable device (PD). The term “portable device” here refers to a portable device/player having functions of expanding and deciphering the compressed and enciphered contents, and playing the contents.
A screening processing system such as shown in FIG. 1 is installed in a calculator system such as a personal computer for example, and is connected with the portable device via, for example, general-purpose bus cables such as i-link or USB (Universal Serial Bus), or near-range wireless data communication such as IrDA (Infrared Data Association) or Bluetooth technology.
Electronic watermarking is an art of inserting additional data in music contents to a degree that the additional data is not audibly perceivable, and generally, around 12 bits of data can be inserted in a period of around 15 seconds.
However, there is a problem in that detecting electronic watermarks is computation-intensive, thereby requiring time. For example, attempting to detect electronic watermarks throughout the entire music contents would require ⅓ to ½ of the actual playing time of the music.
Now, studying an arrangement wherein the above screening processing is installed in a personal computer and music contents are copied from a CD to a portable device, this comprises the following processes:
(1) Data is read out from the CD, and is copied to a hard disk as a WAV format (or other format) file.
(2) The WAV file is inspected, to detect electronic watermarks from the entire music data.
(3) In the event that copy forbidding information of “No More Copy” is detected from the electronic watermark, copy processing of the music contents is terminated at that point. On the other hand, in the event that such copy forbidding information is not detected, the detecting processing is continued to the end of the music piece, and in the event that such copy forbidding information is not detected to the very end, the flow proceeds to the subsequent step (4).
(4) The WAV file is subjected to bandwidth compression by ATRAC3 (Adaptive Transform Acoustic Coding 3), for example.
(5) The data subjected to bandwidth compression is enciphered, and temporarily copied onto a hard disk.
(6) The compressed and enciphered file on the hard disk is transferred to the portable device.
Here, despite the fact that screening an attempted copy from a conventional CD to which no watermark has been inserted is meaningless, all data is consequently checked in the above step (3), taking extra time for detecting. This would be very unhandy in the event that the user is attempting to hurriedly copy a favorite piece of music from a CD to a portable device before leaving home, for example.